Method of extending the utility of an integral driving-sensing pot-core half eddy current probe

ABSTRACT

An axial direction groove is formed in a high permeability toroidal core taking the form of a pot core half with a mounting hole, a high cross-section ratio copper casing being tightly fit around core circumference, having poly-phase excitation windings shuttled thriugh the mounting hole to encompass both the copper casing and the pot-core, forming an integral driving-sensing eddy current probe. A naked pot-core is wound as an integral driving-sensing probe. Poly-phase excitation of the probe is mesh-connected as a gramme-ring.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This Patent Application is a continuation-in-part of patent application Ser. No.: 09/419,140 filed Oct. 15, 1999 and 09/467,599 filed Dec. 20, 1999, pending payment of Issue Fee.

BACKGROUND ART

[0002] Tesla Pat. No. 382,280 disclosed a ring built up of insulated annular iron plates and wound with poly-phase distributions forming an early rotating field stator for generator/motor use, Field utility was limited to the winding window of the toroidal stator. In the cited Logue patent applications the rotating hemispherical flux fringing from the plane of this toroidal stator (pot-core half) was utilized for inducing eddy currents in conducting workpieces e.g. aircraft splice joints The driving flux is directly coupled from the toroidal plane to the workpiece.

[0003] The preferred pick-up assembly to date is a pot-core half with a pick-up coil of many turns of small guage magnet wire e.g. 42 ga., wound around the central pole, filling the annular coil space. For more complete annular space filling of the pick-up core, flat small guage magnet wire may be spool-less wound, using H. P. Reid Co (trademark). adhesive pre-coated voice-coil wire.

[0004] Alternately multiple parallel smaller gauge magnet wires e.g. 46 gauge, may be used.

[0005] This high-density method of pick-up coil winding accentuates the z-axis permeability modulation of the pot-core half, increasing ramping signal build-up re: Logue Pat. No. 5,909,118. As taught in Logue application Ser. No. 09/467,599 a polar coordinates sensor may be reduced to a ferrite pot-core core (integral x-y-z axes of permeability) having a pick-up coil of many turns wound around the central pole 284 (FIG. 1), combined with a rotating driving field generated by sine-cosine currents flowing sine-cosine excitation windings wound through mounting hole (now a winding hole) 184, in FIG. 1. The pot-core half must be segment-less (no lead slots).

[0006] Oscillatory Signal Build-up

[0007] The polar coordinates signal disclosed in the asending Logue patents is actually formed by succesive revolutions of the hemispherical driving field acceleration; the axis of which is displaced by an asymmetry (flaw) in the eddy current reflection.

[0008] This is a rotary type of parametric pumping.

BRIEF DESCRIPTION OF THE DRAWINGS

[0009]FIG. 1 is a sectional-perspective viewof eddy current probe PS1 spatially illustrating the disclosed methods of increasing resolution.

[0010]FIG. 2, is a block-circular diagram of the preferred excitation/connection method for probe PS1 in FIG. 1.

[0011]FIG. 3, is a perspective-quadrant view of an eddy current probe utilizing concentric integral driving-sensing pot-cores on increasing radii.

OBJECTS OF THE DISCLOSURE

[0012] A primary object of this disclosure is pursuant to the benefit of the filing date of pending Logue application Ser. No. 09/467,599 pertaining to a coil wound in the annular groove formed in a toroidal core i.e. a pot-core half (element 188 in FIG. 1). The referred benefit is found in Section 201.08 (MPEP). In the cited application Ser. No. 09/467,599 described the dual/alternate functions of a coil (190, FIG. 1) wound in the annular groove (179, FIG. 1) were: 1, poloid axis excitation, 2) as an auxiliary pick-up coil for detecting an asymmetry in the hemispherical probe driving field (flaw in a conducting workpiece,) A claim covering this alternate utility was inadvertently left out of application Ser. No., 09/467,599 by the Applicant.

DETAILED DESCRIPTION

[0013] A second object of the disclosure is an improved method of fitting a Lenz lens/caseing 177, in FIG. 1, (a higher cross-section ratio than formerly utilized) around integral driving/sensing core 188, for tighter focusing of the driving field. Previously, (cited Logue application Ser. No. 09/467,599) the copper Lenz lens left a concentric air gap between driving-sensing core and subject high cross-section Lenz lens 177.

[0014] To prevent any cutting of magnet wire insulation Lenz lens is covered with a hard insulating coating.

[0015] Another object of the disclosure is to teach a method of assembling a simple/robust eddy current probe comprising: a pot-core of high permeability, a Lenz reflecting lens and encompassing x-y axes excitation winding distributions. This novel winding method as illustrated in FIG. 1, x-y axes excitation windings 162 a, (show in partial i.e. one quadrant represents all four quadrants) are wound through winding hole 193, encompassing integral driving-sensing pot-core 188, Lenz lens 177, and pick-up coil 190. Winding connections to all four quadrants are symbolized by leads Ea. 162 a are An alternate method of excitatation winding 162 b (drawn in partial by dashed lines), which is toroidal wound through mounting hole 193 having leads Eb. For signal nulling pick-up coil 190 (having leads SIG. a) is precision wound around cylindrical pole 184 filling annular space 179. Pot-core half 188 has a base portion 185 and an open annular sensing face 166.

[0016] An object of the disclosure is to teach a simple method of signal nulling e.g. under dynamic conditions, the all encompassing excitation winding turns 162 t, are individually adjusted (angularly shifted slightly) for a near flat-line null on an oscilliscope, and then glued in place. Further the described probe assembly may be encased in a cylindrical metal/plastic housing, and set in a potting compound (a thin layer covering the annular sensing face 166.)

[0017] An object of the invention is an improved method of sine-cosine excitation connection configuration (including series resistors in each lead to a bipolar excitation source (FIG. 2)

[0018] Preferred Core Materials 1) Integral driving/sensing toroids: Square Permally 80, Supermalloy (tape wound), from MAGNETICS* Butler, Pa.

[0019] 2) Pot-core half: Ferrite part no. 5578000721i, from Fair-Rite Products Corp. Wallkill, N.Y.

[0020] Method of Driving Excitation and Connections

[0021]FIG. 2, digrammatically illustrates a preferred method of: 1) sine-cosine excitation windings 162 a, FIG. 1, (connections in the probe case and to the excitation source EXx.) The preferred method of connecting configuration of poly-phase excitation windings 162 a, FIG. 1, is a mesh-connected (a single winding 62 a, FIG. 2, is continously wound the circumference of toroid 88 a) being tapped at each quadrant (x-axis taps are LXa, LXb, and y-axis taps are LYa, LYb.) This method allows the currents flowing through windings 162 a, FIG. 1, to circularly equalize as in a gramme-ring GR, FIG. 2 increasing eddy current resolution and also allowing a greater probe tilt angle (signal has less tilt noise). Referring again to FIG. 2, Current Lo the quadrant taps LXa, LXb, LYa, LYb, are respectively fed through series resistors XRa, XRb, YRa, YRb, for enhanced differential x-y axes tilt-ability e.g. a probe tilt toward quadrant Qa, results in an increase of eddy current reflection in quadrant Qa. The gramme-ring, being a series circuit allows a differential (diametric) current-shift toward quadrant Qb. Quadrants Qc, Qd, respond to tilt in their directions in a likewise redistribution of exitation currents. Digital values of the predetermined poly-phase sinusoidal wave shapes are loaded into the HOST COMPUTER on bus 05. The computer generated digital values are fed to plural digital-to-analog converters DAC (PLURAL) by bus 06. The analog waveforms are carried by buses 01-04 to the x-y axes amplifiers Xa, Xb, Ya, Yb, and from there to the respective series resistors XRa, XRb, YRa, YRb.

[0022] Concentric Pot-core Halves

[0023] The light of cited Logue application Ser. No. 09/467,599 combined with the present teachings on integral driving-sensing pot-cores wound according to the discription, obviously pot-cores of increasing radii may be disposed concentrically as shown in FIG. 3 (a perspective-quadrant view of probe PS2). Eddy current probe PS2, includes in the outer radius wound integral driving-sensing toroidal core 255 a, (a pot-core of enlarged diameter.) Core 255 a is fully circumferentially wound with poly-phase excitation windings 262 a, (leads not drawn) and is formed of a high permeability material with an annular pick-up coil groove 279 a. Core 255 a has outer and central poles 286 a, 284 a. Pick-up coil 290 a in concentrically disposed in groove 279 a (leads not shown) generating a first flaw signal. Integral driving-sensing pot-core 255 b, is formed of a high permeability material, having outer and central poles 286 b, 284 b, leaving an annular pick-up coil space 279 b. A pick-up coil 290 b is wound within groove 279 b for generating a second flaw signal. Polyphase windings 262 b are wound around core 255 b.

[0024] Contemplated Excitation Methods

[0025] Just as a toroidal deflection yoke around the neck of a TV picture tube magnetically moves the electron beam/s to any location on the screen according to a predetermined program, so also the subjec As part of this disclosure, an eddy current scan pattern similar to television raster may be generated in a planar workpiece by the polar coordinates probe utilizing a programable (software) method. Radar display type scans e.g. plan-position indicator (ppi) is also covered as a programable method of eddy current excitation for extending resolution (both cylinder and planar workpieces). It is contemplated the preceding methods would be useful for detecting aircraft flaws. 

We claim:
 1. A method of extending utility; in a toroidal plane sensing face eddy current probe for detecting a flaw in a conducting workpiece by means of detecting an asymmetry in a rotating hemispherical driving field, said probe comprising: a torus core formed of a high permeability material having a poloidal coil space, and; said torus core further formed with an annular groove extending axially from the poloidal coil space to the core surface, said core taking the shape of a pot-core half, and; poly-phase excitation winding distributions wound through the toroid window to symmetrically cover the core surface; ramping poly-phase excitation currents being applied to the said excitation winding distributions for inducing a rotating driving dipole, fringing from the toroidal plane, for inducing a hemispherical eddv current pattern in said workpiece; a poloidal coil being wound concentrically within the said poloidal coil space, and having connecting leads; the said method of extending probe utility comprising: utilization of the said poloidal coil as a pick-up coil as the said means for detecting an asymmetry in the rotating hemispherical driving field; said pick-up coil shunted by a variable capacitor to form an oscillatory Lank circuit for building up a flaw signal.
 2. Method of increasing eddy current resolution; in a toroidal plane sensing face eddy current probe for detecting a flaw in a conducting workpiece by means of detecting an asymmetry in a rotating hemispherical driving field, said probe comprising: a toroidal core formed of a high permeability material taking the shape of a pot-core half, and; said pot-core half further comprising: a central cylindrical pole, concentrically surrounded by a cylindrical outer pole, leaving an interposed annular pick-up space, and a base portion for connecting these two poles at one end, a cylindrical winding hole concentrically disposed in the central cylindrical pole, and extending the axial length of the pot-core half, the opposite end forming an annular sensing face, and; a pick-up coil of many turns wound around the central pole for the detecting the said asymmetry in the driving field and generating a flaw signal; said pick-up coil shunted by a variable capacitor to form an oscillatory tank circuit for building up a flaw signal; poly-phase excitation winding distributions, having connecting leads wound through the said winding hole, and around the outer pole to symmetrically cover the pot-core half circumference, forming an integral driving-sensing assembly; a high reluctance non-ferrous cylindrical case concentrically surrounding the integral driving-sensing assembly, and ramping poly-phase excitation currents being applied to the said excitation winding distributions for inducing a rotating driving dipole, fringing from the toroidal plane, for inducing a hemispherical eddy current pattern in said workpiece; the said method of increasing eddy current resolution comprising the steps of: i) tightly fitting the high reluctance non-ferrous cylindrical case coaxially around the said pot-core half, before winding the said excitation winding distributions as to encircle the said case, the pot-core radius, and the pick-up coil radius, for tighter focusing of said driving field, providing the said increased resolution; iii) said excitation winding distributions being mesh-connected as a gramme-ring configuration for a more circular driving field and less tilt error.
 3. The method according to claim 2, wherein the said mesh-connected gramme-ring is configurated for a 3 phase excitation source.
 4. The method according to claim 2, wherein the said mesh-connected gramme-ring is configurated as a four pole 2-phase motor stator for one rotation of the said driving field during two complete cycles of a sine-cosine excitation source. 